Project Summary/Abstract Posttraumatic stress disorder (PTSD) commonly co-occurs with alcohol use disorder (AUD), affecting 30-60% of those seeking AUD treatment, and may be especially salient for women with AUD. AUD patients with comorbid PTSD have poorer outcomes following treatment, including earlier relapse, greater substance use, and poorer psychosocial functioning, compared with those without PTSD. Although there are a small number of evidence-based psychotherapies that may reduce PTSD symptoms, men and women in AUD treatment rarely receive them, even in residential AUD settings. Barriers related to cost, time, and clinician expertise severely limit the availability of PTSD interventions in AUD treatment settings. Consequently, there is great need for low-cost, primarily self-guided, and scalable PTSD treatments that can be delivered within existing AUD treatment structures. PTSD Coach is a promising mobile health (m-Health) application (app) that could address treatment gaps for men and women with AUD and comorbid PTSD. Recent preliminary data from a community sample of individuals with PTSD symptoms, without inclusion criteria related to alcohol use, showed that the group randomly assigned to use the app had significantly greater improvements in PTSD symptoms relative to those in a waitlist control (Cohen?s d=0.41), and a further pilot showed that brief clinical app support/facilitation (i.e., 4, 20-minute sessions) may boost these treatment effects. Despite its potential to improve both PTSD and alcohol-related outcomes, PTSD Coach with brief clinical support has not been tested as a treatment for patients with comorbid PTSD in the AUD treatment setting. Therefore, the objectives of this project are to test whether the use of the PTSD Coach app intervention package (PTSD app + brief support) in the residential AUD treatment setting can improve PTSD symptoms, and help sustain AUD treatment gains during recovery. Given that prior research has found AUD-, PTSD-, and treatment-differences between men and women, the proposed study will also evaluate potential differences in treatment effects between men and women. To accomplish these goals, we will randomize 150 men and 150 women (total n=300) with AUD and co-occurring PTSD in residential addictions treatment to either the PTSD Coach intervention package or the enhanced usual care (EUC) control. All participants will complete a baseline assessment and follow-ups at 1- (post-treatment),3-, 6-, and 12-months post-randomization. Delivering the PTSD Coach intervention during residential AUD treatment provides an ideal opportunity for patients to benefit from the app during a period of relative stability. This project is significant because it targets a comorbid, high-needs AUD treatment population, improves access to care, and utilizes an m-Health intervention approach that is readily scalable. Incorporating a promising, publicly available PTSD app into AUD treatment to address co-morbidity among AUD patients is highly innovative. The findings from this study could have substantial public health impact by improving treatment outcomes for patients with AUD and comorbid PTSD.